1. Field of the Invention
This invention relates to an oil pressure switch failure detection system for an outboard motor, particularly to a system for detecting failure of a pressure switch(es) that generates an output in response to the pressure of engine oil (lubricant) to be supplied to an internal combustion engine for an outboard motor for small boats.
2. Description of the Related Art
An outboard motor has an oil pressure switch(es) or sensor(s), installed at an appropriate location of a hydraulic circuit of the internal combustion engine or of an oil pan, which generates an ON signal when the oil pressure drops below a predetermined operating point and when the ON signal is generated, it warns to the operator and controls the fuel injection amount and ignition timing so as to decrease the engine speed to a level under which the engine is not suffered from damages such sticking or wear due to metal-to-metal contact.
If such an oil pressure switch or sensor fails, when the oil pressure is, in fact, sufficient, the oil pressure could nevertheless be determined to be abnormal. Or, the abnormality of oil pressure could be overlooked.
An object of the present invention is therefore to solve the aforesaid problems by providing an oil pressure switch failure detection system for outboard motor, which can accurately detect failure of an oil pressure switch which generates an output in response to the pressure of engine oil to be supplied to an internal combustion engine for an outboard motor for small boats.
For realizing this object, the invention provides a system for detecting failure of oil pressure switches which generate signals in response to a pressure of oil to be supplied to an internal combustion engine for an outboard motor for small boats, comprising: a first oil pressure switch which generates a signal indicating that the oil pressure is less than or equal to a first predetermined oil pressure; a second oil pressure switch which generates a signal indicating that the oil pressure is less than or equal to a second predetermined oil pressure which is set higher than the first predetermined oil pressure; switch signal discriminating means for discriminating whether the generated signals of the first and second oil pressure switches are equal to be expected signals expected under operating conditions of the engine; and switch failure determining means for conducting a determination as to whether at least one of the first and second oil pressure switches fails based on a result of discrimination of the switch signal determining means.